The Quanto programme (http://biostats.usc.edu/Quanto.html) was used for power calculations before the main analysis. The statistical power of the analysis is enough to find the main effect of the 5-HTTLPR polymorphism with an assumed R2=1% explained variance in an additive heritability model by 99% probability. In addition, it has 99% power to find interaction between continuous interacting environmental effect RLE and 5-HTTLPR with assumed additive heritability and R2=1% explained variance.
